Please note before buying this model selespeed.
The most trouble with the alfa 156 is the selespeed actuator packing up this will cost from alfa over £1000.00 last year mine suffered this problem and i spent out on paying for a new actuator only to find it needed to go on the examiner "further expense and recovery costs to alfa" then to find out my selespeed ecu was playing up so that needed to be remapped reprogrammed basically.
If you see a cheap selespeed on the internet and you want to buy it check the following out first.
Does the car drop into any other gears or wont select other gears in a way it shouldnt does it stall?
Does the selespeed warning light flash?
Are the gears smooth when changing ?
See the car definately see it before buying test it from flat cold and once first started select first gear ensure the gear indicator isnt flashing and change up and down the gears.
You would be mad buying one anyway but please check before purchasing has they can have serious failure despite maintenace and servicing regular.
Please check out alfa owner dot com they are a must when you own an alfa and they are a great forum with the best info around and will advise on even further problems they suffer.
Good luck and remember to check or it will cost you massively in the long run.